Writing positive (and true) Yelp reviews is a great way to start a conversation with a prospective advertiser.
Most great businesses pay attention to their Yelp reviews and see it as a channel that can drive customer traffic.
The owner or marketing manager will often comment or message you thanking you for the review. This gets you the decision maker’s name if you did not already have it and you can message them directly via Yelp.
When you do talk advertising, the persuasion psychology principle of Reciprocity is in play. You did them a huge favor, now it’s their turn.